Conventional internal combustion engines utilize air throttling device and timing devices. The throttle device or valve is actuated by a driver depressing and/or releasing the gas pedal, and regulates the air flow to the intake valves. The engine intake valves are driven by the camshaft of the engine. The intake valves open and close at predetermined angles of camshaft rotation to allow the descending piston to draw air into the combustion chamber. The opening and closing angles of the valves and the amount of valve lift is fixed by the cam lobes of the camshaft. The valve lift profile (i.e., the curve of valve lift plotted relative to rotation of the camshaft) of a conventional engine is generally parabolic in shape.
Modern internal combustion engines may incorporate more complex and technologically advanced throttle control systems, such as, for example, an intake valve throttle control system. Intake valve throttle control systems, in general, control the flow of gas and air into and out of the cylinders of an engine by varying the valve lift timing, amount of lift and/or duration (i.e., the valve lift profile) of the intake valves in response to engine operating parameters, such as, for example, engine load, speed, and driver input. Intake valve throttle control systems vary the valve lift profile through the use of various mechanical and/or electro-mechanical configurations, generally referred to herein as variable valve actuating (VVA) mechanisms. One example of a VVA mechanism is detailed in commonly-assigned U.S. Pat. No. 5,937,809, the disclosure of which is incorporated herein by reference.
Conventional VVA mechanisms generally include a link which connects the input rocker arm of the mechanism with the output cam of the mechanism. The use of a link increases the size of the VVA mechanism, and thus a larger space is required in order to install the VVA mechanism within the engine. The link is typically coupled to the input rocker arm and the output cam with joints and/or pins. Thus, the use of a link requires additional component parts and thereby makes the VVA mechanism relatively complex from a mechanical standpoint. The many component parts increase the cost of the mechanism and make the mechanism more difficult to assemble and manufacture. The joints and pins of a conventional VVA mechanism are subject to interfacial frictional forces which negatively impact durability and efficiency. The link adds to the oscillatory mass of the VVA mechanism, and thereby limits the effective engine operating range within which the VVA mechanism can be used.
Therefore, what is needed in the art is a VVA mechanism having fewer component parts, thereby reducing cost and complexity of the mechanism.
Furthermore, what is needed in the art is a VVA mechanism with fewer joints and/or pins, thereby reducing interfacial frictional losses and increasing the durability of the mechanism.
Even further, what is needed in the art is a VVA mechanism having reduced package size.
Still further, what is needed in the art is a VVA mechanism having a reduced oscillating mass to thereby enable the mechanism to operate across a wider range of engine operating conditions.
Moreover, what is needed in the art is a VVA mechanism that eliminates the link, thereby reducing the overall size, reducing interfacial frictional losses, and reducing the oscillating mass of the mechanism.